Structure
Pectin is a complex polysaccharide consisting mainly of esterified D-galacturonic acid resides in an alpha-(1-4) chain. The acid groups along the chain are largely esterifed with methoxy groups in the natural product. There can also be acetyl groups present on the free hydroxy groups. The galacturonic acid main chain also has the occasional rhamnose group present which disrupts the chain helix formation.
Pectin is a complex polysaccharide consisting mainly of esterified D-galacturonic acid resides in an alpha-(1-4) chain. The acid groups along the chain are largely esterifed with methoxy groups in the natural product. There can also be acetyl groups present on the free hydroxy groups. The galacturonic acid main chain also has the occasional rhamnose group present which disrupts the chain helix formation.
Pectin is also known to contain other neutral sugars which are present in side chains. The most common side chain sugars are xylose, galactose and arabinose. The sidechains tend to occur in groups and have led to the description of the pectin molecule as having hairy and smooth regions.
Commercially pectins are categorised according to their methoxy content and wether they from gels quickly or slowly. Roughly speaking pectins can be split in to high methoxy pectins (>50% esterified) and low methoxy pectins (<50%esterified). Low methoxy pectins can also be amidated or not.
Additional information on pectin sources and properties can be accessed using the arrows in the Further Reading box below.